Pumping unit with improved flexibly connected beam



Aug. 18, 1964 J. E. LOTT 3,144,778

PUMPING UNIT WITH IMPROVED FLEXIBLY CONNECTED BEAM Filed April 5, 1962 aSheets-Sheet 1 JOHN EDWARD LOTT INVENTOR A T TORNE Y Aug. 18, 1964 J. E.LOTT 3,144,778

PUMPING UN IT WITH IMPROVED FLEXIBLY CONNECTED BEAM Filed April 5, 19623 Sheets-Sheet 2 FIG. 7. FIG. 1/.

JOHN EDWARD LOTT INVENTOR ATTORNEY Aug. 18, 1964 J. E. LOTT 3,144,778

PUMPING UNIT WITH IMPROVED FLEXIBLY CONNECTED BEAM Filed April 5, 1962 5Sheets-Sheet 3 FIG. I3.

FIG. I4.

JOHNEDWARD LOTT INVENTOR ATTORNEY United States Patent PUMPING UNIT WITHTMPROVED FLEXIBLY CONNECTED BEAM John Edward Lott, Fort Worth, Tex.,assignor to American Manufacturing Company of Texas, Fort Worth, Tex., acorporation of Texas Filed Apr. 5, 1962, Ser. No. 135,267 1 Claim. ((31.74-41) This invention relates to well pumping units and has reference toan improved spring linkage between the walking beam and the speedreducer. This application is a continuation in part of my copendingapplication, Serial No. 158,518, filed December 11, 1961, now US. PatentNo. 3,109,313, which issued November 5, 1963.

The referred to copending application is directed to a 100%geometrically efiicient unit operable in either direction of rotation ofthe cranks. Generally, the construction of the copending application iscomprised of a spring linkage connected with the extending end of thepitmans and coactive with an arcuate surface on the oscillating walkingbeam. The are of said surface is generated about the axial center of thesaddle bearing. While such construction provides 100% geometricefficiency, this linkage, by selecting a fixed direction of rotation ofthe cranks, can be arranged to effectively reduce the torque variationsat the speed reducer. Generally, such reduction of torque variation isaccomplished by canting the arc of the rear mule head and therebyfavoring the power source by reason of the inherent geometry of thelinkage. A longer lever arm is provided during the up stroke when thewell load is at its maximum, and a shorter lever arm is provided on thedown stroke to aid the lifting of the counterbalance weight.

Accordingly, an object of the invention is to provide a pumping unitwherein torque variations are reduced at the speed reducer byeffectively providing a longer lever arm during the up stroke and aneffectively shorter arm during the down stroke.

Additional objects include the elimination of certain wearing parts suchas the tail bearing, oil seals and flexible lubrication lines.

These and other objects will become apparent from the followingdescription and the accompanying drawings, wherein:

FIGURE 1 is a side elevational view of a pumping unit in accordance withthe invention.

FIGURE 2 is an end elevational view of FIGURE 1.

FIGURE 3 is a fragmentary perspective view of the flexible connection ofthe pitmans with the rear mule head.

FIGURES 4 through 11 are schematic views illustrating one completerevolution of the cranks and show the directions of forces applied tothe walking beam by the pitmans.

FIGURES 12 through 15 are also schematic views and illustrate theapplication of certain formulas hereinafter referred to.

The pumping unit illustrated is conventional with respect to its generalconstruction and includes a base 10, a samson post 11 and a walking beam12 mounted on the samson post by means of a saddle bearing 13. At theforward end of the walking beam 12 there is a mulehead 14, hereinreferred to as the forward mulehead, bridle 15 which is attached to thepolished rod 16 by a grip 17.

4 3,144,778 Patented Aug. 18, 1964 "ice Mounted on a conventional speedreducer 18 there is a drive pulley 19 on a driven shaft 20 and also adouble pitman crank 21 on the crank shaft 22. The pitmans 23 areattached to the cranks 21 by wrist pins 24. Counterweights 25 aremounted on the cranks 21 in the usual manner.

A mulehead 26 with an arcuate bearing plate 27 integral with its body 28is mounted on the rear end of the walking beam 12 so that its arcuatesurface is concentric with a point or points near the saddle bearing 13.As hereinafter described, the purpose of the bearing plate 27 is to makethe rear mulehead 26 wider than a conventional mulehead, such as theforward mulehead 14.

A clamp 29 with bolts 30 threaded intothe bearing plate 27 at its upperend provides an attachment for depending spring steel actuating plates31 perforated at their upper ends to receive the bolts 30. The plates 31are in side-by-side relation, but a single plate, not shown, may beemployed. The plates 31 are similarly perforated at their lower ends toreceive other bolts 32 by means of which the plates are clamped betweenthe two halves of an equalizer beam 33 which connects the two pitmans attheir upper ends. The equalizer beam 33 could be combined with the twopitmans 23 into a solid inverted U-shaped member, but in order torelieve stresses created by slight misalignments of the cranks it hasbeen found to be advantageous to connect the equalizer beam 33 to thepitmans by means of spring steel plates 34 held to the ends of theequalizer beam 33 by clamps 35 and bolts 36 through matching holes inthe plates, and likewise to the upper ends 37 of the pitmans 23 by bolts38 through holes in the lower ends of the plates 34.

The arcuate surface of the bearing plate 27 is generated about a point39, or multiple of points, not shown, above the axis of the saddlebearing 13 as indicated by the dash line arrow 40. Thus, the rearmulehead 28 is canted downwardly and inwardly relative to the saddlebearing 13, whereas the forward mulehead 14 has its arcuate surfacegenerated about the axis of said bearing in the usual manner. As willbecome apparent, when the rear mulehead 28 is so canted, it is necessarythat the cranks 21 rotate counterclockwise as viewed in FIGURE 1. InFIGURE 1 the arrow lines 41 and 42 indicate the extreme inclination ofthe walking beam 12 at the ends of the pumping stroke.

In the operation of the pumping unit, schematically illustrated inFIGURES 4-11, inclusive, which show progressively one completerevolution of the crank 21, it is apparent that during the downstroke ofthe pitman 23, which is equal to the lift of the polished rod 16, theeffective lever arm of the walking beam 12, indicated by the arrow line43, is substantially longer than the lever arm on the upstroke indicatedby arrow line 44 in FIGURE 10. This gives the power source a mechanicaladvantage during that part of the cycle requiring the greater effort.

This difierence results also in a slower lift stroke on the pump and afaster return stroke which improves the operation of the pump andreduces wear. Further, it can be seen from the diagrams that thedirection of the force exerted by the pitman 23 during its downstroke isapproximately normal to the theoretical lever arm 43 for a large part ofthe cycle as shown by its closely parallel relation to the perpendicular45.

On the other hand, during the upstroke of the pitman 21, if it werepivotally connected in the conventional manner to give the samemechanical advantage in the downstroke as shown in FIGURES 4-7, it wouldmake the very disadvantageous angle :1 (FIGURE with the lever arm 43instead of the advantageous angle b with the theoretical lever arm 4-4which results when the canted mulehead 26 is employed.

The advantage gained by the use of the canted rear mulehead 26 isfurther proven by the following formulas applied to FIGURES 12 to 15,inclusive, in which FIG- URE 12 represents the unit with the cantedmulehead on the upstroke of the pitman and FIGURE 13 represents the sameunit on the downstroke of the pitman.

IN FIGURE 12 Dowlzstroke PT 11 (F YR) F --U D CB P1 P1 R 2E1 IN FIGURE13 U pstroke EQUATING PTU=PTD Now assume following well conditions, andsolve for counterbalance and peak torque:

= 8600 X 24 06,400 in lbs.

UNIT PEAK TORQUE Downstroke PT =206,400 [6000 XggJQi 205,400 1 72,80033,500 in lbs.

Upstroke PT :10,000 X 24206,400=33,600 in lbs.

Applying similar formulas to FIGURES l4 and 15, representingconventional unit having corresponding dimensions, but in which a rigidpitman 46 is pivotally attached to the walking beam, We have:

PT= [10300-8000]? ECB= 6000+ 2000=8000# in lbs. (Upstrolre ordownstroke) Thus, by comparison, the invention requires onlyapproximately of the power required for a comparable conventionalpumping unit. Additionally, a smaller and therefore less expensive speedreducer may be used.

The invention is not limited to the construction herein shown anddescribed, but may be made in various ways within the scope of theappended claim.

What is claimed is:

In a beam type pumping unit:

a beam pivotally mounted for oscillation in a vertical plane,

forward and rear muleheads mounted on the ends of said beam, saidmuleheads having outer generally vertical arcuate surfaces, the arcuatesurface of said rear mulehead being generated about at least one pointabove the axis of oscillation of said beam,

a crank beneath said rear mulehead, said crank having an extending endrotatable about the remaining end, said crank rotating in a directionsuch that said extending end moves upwardly when on the side of rotationadjacent said forward mulehead,

a pitman journalled on the extending end of said crank and extendingupwardly therefrom, and

flexible means connected at the upper end of and extending over thearcuate surface of said rear mulehead and connected with the upper endof said pitman.

References Cited in the file of this patent UNITED STATES PATENTS1,888,530 Goble Nov. 22, 1932 1,945,774 Goble Feb. 6, 1934 3,005,353Gallaway Oct. 24, 1961

